Flashcards for the Record of Time
Topics 2-3:  Overview of Dating and Relative Techniques
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The term for a date that places an event in its chronological position with reference to a universal time scale such as a calendar. Such dates usually are given in terms of the number of years before or after a calendar starting point. For instance, 1950 B.C. was 1950 years before the beginning date of the Gregorian calendar, which is commonly used today.

chronometric date

The term for a date that gives the time of an event only with reference to another event that is not worldwide in scale. It only indicates that one event occurred earlier or later than another. For instance, the observation that strata 2 is younger than strata 1 beneath it in a geological deposit does not provide information about how many years ago strata 2 was laid down. It only indicates its age relative to strata 1.

relative date

A kind of chronometric date that is measured in years before the present. By convention, scientists have assigned 1950 A.D. in the Gregorian calendar as the present.

B.P. date

The idea that if there are layers in a sedimentary deposit, those laid down first will be on the bottom and those laid down last will be on the top. This principle is the basis for one of the commonly used relative dating techniques.

principle of superposition

The study of geological strata, or layers of rock or soil, usually for relative dating based on the principle of superposition.


The term for breaks in the original stratigraphic sequence of a geological deposit. Understanding all of these changes in an area is a prerequisite for using stratigraphy for relative dating purposes.

unconformity or geological unconformity

The idea that if two objects are found undisturbed in the same strata of a site, they very likely date to the same time period. This principle can be used for relative dating purposes.

principle of association

A term referring to the position in a site where an object was originally deposited. Finding an artifact or fossil undisturbed in this way allows a researcher to apply the principle of association in dating and interpreting it. This can not be done if the object is in a secondary context, which is to say that it was moved to a new location after the original deposition.

primary context

The remains of a plant or animal of a species that is known to have lived only during a specific time period. The discovery of such a fossil in an archaeological site is circumstantial evidence of the approximate time period that it was occupied. These fossils can be used to relatively date the remains of our ancient ancestors if they were found in association with each them.

index fossil

The name for the relative dating technique that is based on the discovery of index fossils.


A relative dating method based on the fact that bones buried in the ground progressively lose nitrogen and gain fluorine and other trace elements. If two bones from the same site have markedly different amounts of nitrogen and fluorine, it is a strong indication that they did not come from the same time period. The bone with the least amount of nitrogen and the greatest amount of fluorine is most likely the oldest.

fluorine analysis dating

The name of a presumably very ancient human skull and jaw found in England in 1912 by Charles Dawson. As a result of fluorine analysis testing in the early 1950's, this fossil was found to be an elaborate hoax.

Piltdown Man hoax